Method and apparatus for separating a protein membrane and shell material in waste egg shells

ABSTRACT

A method and apparatus for abrading the membrane portion of waste egg shells from the hard mineral portion thereof, is provided. The linking structure between the membrane and shell is initially abraded such that the membrane particles and shell particles can be passively dissociated thereafter.

CLAIM OF PRIORITY

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/757,988 filed Jan. 10, 2001 now abandoned; which is acontinuation of Ser. No. 09/040,563, filed Mar. 18, 1998 now issued asU.S. Pat. No. 6,176,376, issued Jan. 23, 2001 and claims benefit of Ser.No. 60/040,816 filed Mar. 18, 1997.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for efficientlyand simply separating a membrane from the inside of egg shells, and, inparticular, a method and apparatus for separating a protein membranefrom waste egg shells.

2. Description of the Related Art

Nearly 30% of all eggs consumed today in the United States are used tomanufacture processed egg products that are used as ingredients in otherprocessed foods and various food service operations. For example, thealbumen (“egg white”) and egg yolk may be recovered to manufactureliquid egg products of various types. In other instances, the albumenand egg yolk may be dried to form a more shelf-stable product (e.g.,powdered eggs).

The use of eggs by the processed egg sector of the industry isincreasing markedly, according to the United States Department ofAgriculture. In 1984, the egg processing industry utilized 25.6 millioncases of eggs to manufacture liquid and dry egg products. In 1995, 47.5million cases of eggs were utilized. Estimates for 1997 indicate thatmore than 50 million cases of eggs were utilized in a variety of furtherprocessed egg products.

The waste egg shells amassed from such processing are usually subjectedto further processing (e.g., such as with a centrifuge) in order torecover residual albumen which adheres to the egg shells, which can besold to the pet food industry. Nevertheless, the egg shells, whetherfurther processed or not, are largely disposed of as a waste product.

Based on 1997 estimates, therefore, more than 120,000 tons ofunprocessed egg shell waste were generated. More specifically, a surveyconducted in collaboration with the United Egg Producers indicated thatalmost 50% of U.S. egg producers each generate 1000 to 3000 tons of eggshell waste each year. Among the survey respondents, 26.6% used the eggshell waste as fertilizer, 21.1% used it as a feed ingredient, 26.3%disposed of it in dumps as waste, and 15.8% put it to “other” use(s).Among the respondents identifying disposal costs, almost three-quartersreported disposal costs between $25,000 and $100,000 per year. In viewof the significant disposal costs for what is conventionally totally awaste product, and additionally, in view of current environmentalpracticalities which are decreasing the availability of local disposalsites (thereby further increasing disposal cost), it will be readilyappreciated that finding a significant use for egg shell waste wouldhave important financial and environmental, benefits.

It is well-known that the egg shell of a chicken, comprises an inorganicexternal mineral portion and an internal organic matrix upon which themineral portion is built. The mineral portion is primarily calciticcalcium carbonate. The organic matrix generally comprises an inner andouter membrane layer, each of which are comprised of a network ofproteinaceous fibers, upon which the mineral portion of the shell isformed.

The presence of hydroxyproline in hydrolsates of the membrane layerssuggest that the membrane layers include collagen as a component of thefiber structure. Biochemical and immunological testing has confirmedthis. It has been established that of the total proteinaceous content ofthe membrane structure of an egg shell, about 10% is collagen.

Moreover, genetic collagen variants have been identified in the shellmembranes, with the outer shell membrane being predominately type I andthe inner shell membrane being types I and V. In addition, type Xcollagen has been found in both the inner and outer shell membranesthrough immunohistochemical analysis. It is important to recognize thepresence of collagen in eggshell membranes because of its potentialmonetary value.

The presence of collagen in the shell membranes is interesting becauseof the increasing demand for collagen. Bovine, and to a lesser extent,human, collagen is becoming relatively commonly used in a variety ofapplications, especially in the biomedical field. For example, acollagen glue made from human collagen is known for filling cornealwounds. Also, research in ongoing in producing skin and tissuereplacement products made from collagen. Unfortunately, the cost of suchcollagen based products is very high (at least about $1,000 per gram, orabout $454,000 per pound), although such costs are consideredeconomically acceptable, at least in medical applications, in view ofthe overall cost of medical treatment.

Based on estimates for 1997 egg consumption, as discussed above,approximately 120,000 tons of egg shell waste would yield 110,000 tonsof egg shell and 10,000 tons of membrane. Taking into account that about10% of the membrane is collagen, this would yield 1,000 pounds ofcollagen.

In addition, use of bovine collagen raises an issue as to the possibletransmission of bovine spongiform encephalopathy (commonly known as “madcow disease”). Although, as a practical matter, the risk of mad cowdisease transmission is very small, the mere perception of possible riskcreates a need for private, well-isolated, and expensive herds.

Another problem with bovine collagen is the risk of autoimmune andallergic reactions caused thereby, since approximately 2% to 3% of thepopulation is allergic in this regard. Although, this would appear to bea small percentage, the problem is likely to increase as the use ofbovine collagen products becomes more common.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a method and apparatus for simply and economically separatingthe membrane layer(s) from the inside of waste egg shells, therebypermitting use of both the “clean” egg shells (i.e., egg shellsseparated from the membrane) and the membrane in further applications.This simultaneously diminishes the environmental impact associated withwaste egg shell disposal while offering economic benefit from use of theresultant products.

In particular, it is an object of the present invention to provide anespecially simple method and apparatus, as discussed above, therebyreducing costs for the operation thereof, which, in turn, maximizes theeconomic benefit gained therefrom.

In keeping with the aforementioned objects of the invention, aseparating apparatus according to the present invention includes,generally, a tank holding a liquid. The tank preferably contains plainwater, which is relatively inexpensive and environmentally “friendly.”The separating apparatus also may include a reducing device for yieldingegg shell waste particles of a certain size. Once the waste egg shellparticles are conveyed into the tank, the egg shell particles andmembrane particles attached thereto passively dissociate from oneanother. The egg shell particles, being heavier than the membraneparticles, settle on the bottom of the tank where, generally, they arecollected and delivered to a recovery device. The membrane particles arerelatively light and therefore tend to remain suspended in the liquid inthe tank. According to one aspect of the present invention, liquidcontaining the suspended membrane particles is removed from the tank andthe membrane particles are at least dewatered, thereby yielding a moistbulk membrane product which can be further processed.

A method according to the present invention includes, generally, thesteps of processing waste egg shells to yield dissociated egg shellparticles and membranes, directing the waste egg shell particles into atank containing a liquid, thereby separating the waste egg shellparticles into clean egg shell particles and membrane particles,collecting the membrane particles entrained in the liquid, andcollecting and/or drying the clean egg shell particles.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from thedetailed description given hereinbelow and the accompanying drawingswhich are given by way of illustration only, and thus are not limitativeof the present invention and wherein:

FIG. 1 illustrates a system for separating membrane particles from eggshell particles according to the present invention; and

FIG. 2 illustrates a sweep arm mechanism for promoting membrane shellseparation and for collecting clean shell particles, according to thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The foregoing and other objectives of the present invention will becomemore apparent from the detailed description given hereinafter. However,it should be understood that the detailed description and specificexamples, while indicating preferred embodiments of the invention, aregiven by way of illustration and example only, since various changes andmodifications within the spirit and scope of the invention will becomeapparent to those skilled in the art from this detailed description.

The present invention will be described hereinbelow with reference tothe drawings appended hereto.

FIG. 1 illustrates an example of a separating apparatus 100 according tothe present invention.

Generally, separating apparatus 100 includes a tank 102, a reducingdevice 104 for receiving waste egg shells and outputting waste egg shellparticles of a particular size (discussed further below), a firstrecovery device 106 for recovering a first component of the waste eggshells after separation, and a second recovery device 108 for recoveringa second component of the waste egg shells after separation. Both firstand second recovery devices 106 and 108 communicate with tank 102.

More specifically, waste egg shells are received in a hopper 110 fromwhere they are guided into a reducing device 104 whichcharacteristically outputs egg shell waste particles of a particularsize. A particularly preferable range of particle sizes is between about0.5 mm to about 4.0 mm with respect to the largest linear dimension ofeach particle (i.e., the longest edge-to-edge dimension thereof, whethercontinuous or discontinuous).

Reducing device 104 according to the present invention includes,generally, a driving motor (schematically indicated at 104 a) and acutting head (schematically indicated at 104 b). It is a particularfeature of the present invention that reducing device 104 not onlyprovides a cutting action by which waste egg shells are reduced toparticles between 0.5 mm and 4.0 mm, but also provides an abrasiveeffect whereby the linking structure attaching the egg shell membranesto the egg shell is disrupted. This disruption allows the membraneparticles to passively dissociate from the egg shell particles in thesubsequent process that takes place in tank 102 (discussed hereinbelow).

A particularly useful example of a reducing device 104 according to thepresent invention is commercially available from Urschel LaboratoriesInc. under the trademark COMITROL®. The COMITROL® reducing device isknown in the size reduction field, especially in food sciences.

It will be readily appreciated that a different, known reducing devicemay be used according to the invention as long as the aforementionedabrasive effect is still provided (either in the operation of thealternate reducing device or additionally as part of the separatingprocess) to cause the linking structure disruption discussed above.

In a preferred embodiment, the reducing device 104 abrades the membranesfrom the egg shell such that the linking structure is sufficientlydisrupted so that no further active disruption is needed to separate theabraded membrane particle from the egg shell particles. Preferably,after exiting the abrasive reducing device 104, only passivedissociation is required to separate the abraded membrane particles fromthe egg shell particles.

The waste egg shell particles 114 are conveyed from the reducing device104 to tank 102 via a chute or conduit 112. Tank 102 is generally a flatbottomed tank. Its overall volume is highly dependent on the separatingthroughput desired. However, an example of a tank that is usefulaccording to the present invention has a volume of between 80 to 100gallons. Customarily, tank 102 contains at least plain water and,preferably, only plain water at room temperature.

According to the present invention, the waste egg shell particles 114conveyed via chute 112 land in the water held in tank 102. Preferably,chute 112 extends below a surface of the water in tank 102, whereby thewaste egg shell particles 114 are immediately entrained in the waterbelow and away from conduit(s) 122 (for reasons discussed hereinbelow).

Because of the disruption of the linking structure between the egg shelland the membranes caused by reducing device 104, the membrane particles118 become relatively easy to separate from the “clean” egg shellparticles 120, especially as the waste egg shell particles 114 aresubjected to gravity and settle onto the bottom of the tank 102.Substantially all of the waste egg shell particles 114 are passivelydisassociated in this manner into membrane particles 118 and clean eggshell particles 120.

Since the membrane particles 118 are much lighter than the clean eggshell particles 120, the membrane particles 118 tend to stay entrainedin the water a longer time without settling. The clean egg shellparticles 120 tend to settle onto the bottom of tank 102 because oftheir relatively greater weight.

However, some of the membrane particles 118 may become “buried” underclean egg shell particles 120 which have settled on the bottom of tank102. In order to free these membrane particles, (i.e., promote passivedissociation) the particles on the bottom of tank 102 are slowlystirred, using, for example, a sweep arm assembly 116. Sweep armassembly 116 may include, for example, a motor unit 116 a, a shaft 116 bconnected to motor unit 116 a, and a sweep arm 116 c. In a particularexample of a sweep arm assembly 116, as illustrated in FIGS. 1 and 2,drive shaft 116 b is driven to rotate by motor unit 116 a. Drive shaft116 b is in turn connected to a midpoint of sweep arm 116 c, which isdisposed immediately above the bottom of tank Sweep arm 116 c is rotatedvery slowly (e.g., 1 rev/min or less). This rotation disturbs thesettled particles so that the membrane particles 118 are exposed fromamidst clean egg shell particles 120. Since membrane particles 118readily become entrained in the water, this stirring substantiallyrecovers any membrane particles that settle onto the bottom of tank 102.However, due to the slow rotation of sweep arm 116 c, the clean eggshell particles 120 are beneficially not stirred so vigorously that theytoo are swept upward into the water. This would tend to slow the processbecause it depends on the clean egg shell particles settling onto thetank bottom.

The water containing the entrained membrane particles 118 is suctionedout of tank 102 by a water pump 124, via one or more conduit(s) 122. Asillustrated in FIG. 1, the inlet(s) to conduit(s) 122 are locatedrelatively near the water line in tank 102 and relatively spaced apartfrom chute 112, so as to ensure that primarily entrained membraneparticles 118, and not waste egg shell particles 114 or clean egg shellparticles 120, are suctioned out of tank 102. Conduits 122 may be, forexample, 2.0 inches to 2.5 inches in diameter. The membrane-containingwater is, for example, screened on a mesh belt assembly 126 to dewaterthe membrane particles 118. The dewatered membranes are thereaftercollected as a bulk product in a bin 130 or the like for furtherprocessing, such as drying.

The pumping capacity of water pump 124 is dependent on the particularsof the overall system, including, for example, the volume of water inthe tank, the amount of egg shell waste input into the system, and theprocessing capacity of the first and second recovery devices 106 and108. With the aforementioned example of tank 102 containing 80–100gallons of water, pump 124 may have a pumping capacity of, for example,20 gallons per minute.

It will be readily appreciated that the membrane particles 118 can bealso dewatered by any number of conventional methods, such as, forexample, a static screen (comprising, for example, at least two screenshaving different mesh sizes) instead of a mesh belt assembly.

The water collected in the process of dewatering membrane particles 118is preferably recycled by sending it back to tank 102 via conduit 128,which may also be, for example, 2.0 inches to 2.5 inches in diameter.This reduces the resource requirements of the system and thereforereduces the costs of operation.

Moreover, the outlet of conduit 128 is arranged so as to further promotethe passive dissociation of membrane particles 118 and clean egg shellparticles 120. In an example arrangement, as illustrated in FIG. 1, theoutlet of conduit 128 is arranged below the surface (water line) in tank102. This permits the solution of abraded membrane particles 118, eggshell particles 120, and water coming into tank 102 to enter the waterin tank 102 without excessive frothing caused by entrained air, as wouldoccur if the water were poured into tank 102 from above the watersurface.

It will be readily appreciated that the membrane particles 118 need notnecessarily be dewatered, and may alternatively be collected insuspension. However, the water in tank 102 would need to be replenishedaccordingly, in the absence of water input via conduit 128.

As mentioned above, the clean egg shell particles 120, having beenseparated from membrane particles 118, settle to the bottom of tank 102,and are collected and transported to second recovery device 108. In oneembodiment of the present invention, the bottom of tank 102 includes anelongate groove or depression 130 formed therein. Where tank 102 isround, as illustrated by way of example in FIG. 1, groove 130 preferablyextends substantially completely across a diameter of tank 102. A firstauger 132 is disposed in groove 130, and is driven to rotate by at leastone auger motor 134.

In addition to stirring the mix of abraded membrane particles and cleanegg shell particles settled on the bottom of tank 102, sweep arm 116 csweeps clean egg shell particles 120 into groove 130. As seen in FIG. 2,one side of sweep arm 116 c is provided with a brush or rake-likestructure 148, which loosely stirs the membrane and shell particlessettled on the bottom of tank 102 to cause the membrane particles tobecome entrained in the water, as discussed hereinabove. The other sideof sweep arm 116 c may be provided with a flexible blade 150, which maybe made from, for example, rubber or polytetrafluoroethylene, and whichacts as a squeegee to sweep clean egg shell particles 120 into groove130.

It will be readily appreciated that other arrangements for a sweep armmay be provided according to the present invention. For example, a sweeparm (not shown) may be constructed and arranged to sweep back and forthover a bottom of tank 102 in a direction perpendicular to a direction ofextension of the sweep arm. In this instance, a pair of grooves whichare parallel to the sweep arm may be provided at opposite sides of thetank bottom, with each groove being provided with an auger.

The rotation of first auger 132 transports clean egg shell particles 120to a second auger 136, which may be driven to rotate by one of the atleast one auger motors 134 or by another auger motor (not shown). Secondauger 134 is preferably disposed within a conduit 138 or the like, whichis inclined in the manner shown in FIG. 1, whereby clean egg shellparticles 120 are lifted upwardly above the water line in tank 102(although this is not clearly illustrated in FIG. 1). By lifting cleanegg shell particles 120 above the water line, they can be substantiallydrained of water.

Second auger 134 conveys the clean egg shell particles 120 to a hopper140, through which the egg shell particles enter second recovery device108.

Second recovery device 108 may comprise any conventional device by whichthe egg shell fragments are further drained and/or dried. For example,as illustrated in FIG. 1, second recovery device 108 includes aconventional conveyor belt system 142, onto which clean egg shellparticles 120 are dropped from hopper 140. The conveyor belt system 142conveys clean egg shell particles 120 through (under, adjacent, etc.) aconventional drying unit 144, such as radiant heater and/or hot airblower unit. The drying unit 144 raises the temperature within secondrecovery device 108 to, for example, 212° F. to promote drying.

After passing drying unit 144, clean egg shell particles 120 are dumpedoff of conveyor belt system 142 into another hopper 146 from which theegg shell particles are collected, for example, in a bin 148.

It will be recognized that bioactivity, biohazard, and sanitation issuesare important in the method and apparatus disclosed herein according tothe present invention, especially in the presence of wet egg shells andmembrane. Accordingly, it is noted, especially with regard to thestructural elements of the apparatus disclosed herein, that materials ofmanufacture must generally be chosen in accordance with applicableregulatory standards (such those of the U.S. Department of Agriculture).For example, hoppers 110 and 140, conduits and chutes 112, 122, 128, and138 may preferably be made from stainless steel, as are tank 102, augers132 and 136, and drying unit 144.

The invention being thus described, it will be obvious that the same maybe varied in many ways. Such variations are not to be regarded as adeparture from the spirit and scope of the invention, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included within the scope of the following claims.

1. An apparatus for separating a membrane attached to egg shells, theapparatus comprising: a device for abrading the linking structureattaching the membrane to the egg shells, said device constructed andarranged to output abraded membranes and egg shell particles; a tankcontaining a liquid for receiving the abraded membranes and egg shellparticles, said liquid providing an environment whereby the abradedmembranes and egg shell particles passively disassociate such that cleanegg shell particles sink and abraded membranes remain entrained in theliquid; a membrane recovery device communicating with said tank; and anegg shell particle recovery device communicating with said tank.
 2. Theapparatus according to claim 1 further including an agitator constructedand arranged to displace the egg shell particles on a bottom of saidtank, said agitator further constructed and arranged to release abradedmembranes trapped beneath the egg shell particles and to entrain theabraded membranes into the liquid.
 3. The apparatus according to claim 2wherein the agitator is constructed and arranged to release abradedmembranes trapped beneath the egg shell particles and entrain theabraded membranes into the liquid without substantially dispersing theegg shell particles into suspension within said liquid.
 4. The apparatusaccording to claim 2, wherein said agitator is a movable arm provided atthe bottom of said tank.
 5. The apparatus according to claim 2, whereinsaid agitator comprises an aerator.
 6. The apparatus according to claim2, wherein said membrane recovery device comprises: a membrane extractorconstructed and arranged to extract the abraded membranes from saidtank; a suction system for suctioning and conveying the content of saidtank to said membrane extractor; and a return communicating between saidmembrane extractor and said tank, wherein said agitator is said return.7. The apparatus according to claim 1 wherein said device is arranged tooutput abraded membranes and egg shell particles below a surface of theliquid in said tank.
 8. The apparatus according to claim 1, wherein saiddevice is an abrasive reducing device.
 9. The apparatus of claim 8,wherein said abrasive reducing device is a COMITROL® brand reducingdevice.
 10. The apparatus according to claim 1, wherein said membranerecovery device comprises: a membrane extractor constructed and arrangedto extract the abraded membranes from said tank; a suction system forsuctioning and conveying the content of said tank to said membraneextractor; and a return communicating between said membrane extractorand said tank.
 11. The apparatus according to claim 10, wherein saidmembrane extractor comprises a screening device.
 12. The apparatusaccording to claim 11, wherein said screening device includes at leasttwo screens having different mesh sizes, respectively.
 13. The apparatusaccording to claim 11, wherein said screening device comprises a meshconveyor belt.
 14. The apparatus according to claim 10, wherein saidtank includes a clean egg shell particle transport mechanism fortransporting the clean egg shell particles from said tank to said cleanegg shell particle recovery device.
 15. The apparatus according to claim14, wherein said clean egg shell particle recovery device comprises adrying unit for drying the clean egg shell particles transported to saidclean egg shell particle recovery device by said clean egg shellparticle transport mechanism.
 16. The apparatus according to claim 15,wherein said clean egg shell particle transport mechanism comprises anauger device disposed in an elongate groove at a bottom of said tank.17. The apparatus according to claim 1, wherein said tank includes aclean egg shell particle transport mechanism for transporting the cleanegg shell particles from said tank to said clean egg shell particlerecovery device.
 18. The apparatus according to claim 17, wherein saidclean egg shell particle recovery device comprises a drying unit fordrying the clean egg shell particles transported to said clean egg shellparticle recovery device by said clean egg shell particle transportmechanism.
 19. The apparatus according to of claim 18, wherein saidclean egg shell particle transport mechanism comprises an auger devicedisposed in an elongate groove at a bottom of said tank.
 20. A methodfor separating a membrane attached to egg shells comprising the stepsof: processing a size of egg shells so as to yield egg shell particlesand abraded membranes, the egg shells having a linking structure thatattaches the membrane to the egg shells, wherein the linking structureis abraded from the egg shell particles; directing the egg shellparticles and abraded membranes into a tank containing a liquid, theabraded membranes passively dissociating from the egg shell particles byprimarily remaining entrained in the liquid and the clean egg shellparticles settling to the bottom of the tank; collecting the abradedmembranes entrained in the liquid; and collecting the clean egg shellparticles.
 21. The method of claiming 20 further including the step ofstirring the egg shell particles and abraded membranes wherein theabraded membranes are passively dissociated from said egg shellparticles.
 22. The method according to claim 21, wherein the step ofstirring the egg shell particles and any abraded membranes trappedwithin said egg shell particles settled on the bottom of the tank sothat the abraded membranes become substantially entrained in the liquidis accomplished without substantially dispersing the egg shell particlesinto suspension within said liquid.
 23. The method according to claim21, wherein said stirring step comprises agitating the settled clean eggshell particles and abraded membranes with a movable arm.
 24. The methodaccording to claim 21, wherein said stirring step comprises aerating theliquid.
 25. The method according to claim 20, wherein said step ofcollecting the abraded membranes comprises passing the liquid in whichthe abraded membranes are entrained through a screen and returning theresultant clean liquid to the tank.
 26. The method according to claim20, wherein the liquid comprises water.
 27. The method according toclaim 20, wherein the liquid is water.